Dissolution mechanism of magnesium aluminate spinel in copper smelting slag based on the shrinking core reaction models of corrosion

MgAl2O4 spinel is a critical raw material in spinel refractory production. However, the dissolution behavior of the spinel and its interactions with Cu smelting slag have not been previously studied in detail in terms of thermodynamics and kinetics. Therefore, to investigate the interactions of MgAl2O4 spinel in Cu smelting slag, MgAl2O4 spinel was simulated in Cu smelting slag using FactSage. Additionally, the dissolution mechanism of MgAl2O4 spinel in Cu smelting slag was studied via a slag immersion method. It was found that the Fe ions of the Cu smelting slag diffused mutually with the Mg2+ and Al3+ in the spinel, and the final products of the spinel reaction with the slag were ASpinel (Mg1-xFexAl2-yFeyO4) solid solution and liquid slag phases. The dissolution mechanism was consistent with the shrinking core reaction models. In the early stage of dissolution, ASpinel (Mg1-xFexAl2-yFeyO4) was generated at the interface, and the dissolution mechanism was controlled by the rate of solid solution phase generation, with an activation energy of E1 = 153.17 kJ/mol. At the later stage of dissolution, the Fe ions continued to diffuse into the spinel through the solid solution phase, while the spinel dissolved into the slag, and the dissolution mechanism was controlled by the rate of boundary migration of the solid solution phase, with an activation energy of E2 = 110.84 kJ/mol. Meanwhile, this interdiffusion behavior led to an increased liquid viscosity compared to that of the original slag that could further slow slag infiltration. The spinel could absorb Fe ions, rendering it a promising candidate for use in the Cu industry in the field of chromium-free refractories.